United States
Environmental Protection
Agency
Environmental
Research Laboratory
Corvallis OR 97333
Research and Development
EPA/600/S3-89/002 Aug. 1989
&EPA Project Summary
Geographic Information System
Documentation Of Watershed
Data for Direct/Delayed
Response Project — Southern
Blue Ridge Province Database
Dorothy Mortenson
The Direct/Delayed Response Pro-
ject (DDRP) was designed by the U.S.
Environmental Protection Agency
(EPA) within the National Acid Pre-
cipitation Assessment Program
(NAPAP) to predict the long-term re-
sponse of watersheds and surface
waters to acidic deposition. The pur-
pose of the DDRP is to investigate
and distinguish the time scales over
which surface water systems might
change chemically under varying
levels of acidic deposition. The DDRP
is examining a sub-set of watersheds
sampled in the U.S. EPA - National
Surface Water Survey (NSWS). In the
Southern Blue Ridge Province Region
of the United States, 35 watersheds
are under study. The DDRP required
detailed watershed information on
those characteristics thought
important relative to the effects of
acid deposition. This information was
then mapped, then entered into a
Geographic Information System
(GIS). The purpose of this document
is to discuss what protocols,
guidelines, and standards were used
to complete GIS entry of the mapping
data, and what quality control
procedures were used to ensure
accuracy and consistency.
This Project Summary was devel-
oped by EPA's Environmental Re-
search Laboratory, Corvallis, OR, to
announce key findings of the research
project that is fully documented in a
separate report of the same title (see
Project Report ordering information at
back).
Introduction
The Direct/Delayed Response Project
(DDRP) was designed by the U.S.
Environmental Protection Agency (EPA)
within the National Acid Precipitation
Assessment Program (NAPAP) to predict
the long-term response of watersheds
and surface waters to acidic deposition.
The purpose of the DDRP is to
investigate and distinguish the time
scales over which surface water systems
might change chemically under varying
levels of acidic deposition. The DDRP is
examining a sub-set of watersheds
sampled in the U.S. EPA - National Sur-
face Water Survey (NSWS). In the
Southern Blue Ridge Province Region of
the United States, 35 watersheds are un-
der study.
The DDRP required detailed watershed
information on those characteristics
thought important relative to the effects of
acid deposition. Such characteristics in-
clude soils, vegetation/land use, depth to
bedrock, geology, and streams. This in-
formation was mapped by the USDA -
Soil Conservation Service in cooperation
with the EPA or obtained by existing
maps published by the U.S. Geological
Survey. These maps were then entered
into a Geographic Information System
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(GIS). The purpose of this document is to
discuss what protocols, guidelines, and
standards were used to complete GIS
entry of the mapping data, and what
quality control (QC) procedures were
used to ensure accuracy and con-
sistency.
General Procedures
To ensure accuracy and consistency,
the same general QC measures were
taken for each watershed. First, the regis-
tration of the manuscript maps was
checked. Any necessary corrections were
made before proceeding. Second, a
standard allowance for transformation
error was set to control the accuracy of
digital registration. Third, editing software
was used to detect and correct any errors
within a coverage. Next, prelimi- nary
plots were made and overlaid with
the original maps. Any line discrepancies
were corrected before continuing.
Attributes were written on each plot and
then added to the digitized map. The
attributes were checked with the data file
for completeness. The coverage was then
plotted for the final quality check. This
plot was overlaid with the original map
and checked for line and attribute
discrepancies. If an error was found, it
was corrected and any necessary QC
procedures repeated. If no errors were
found, the plot was checked again
individually by another technician. If any
discrepancies were found by the second
technician, they were corrected and any
necessary QC procedures repeated until
both technicians agreed the final plot to
be accurate.
After the data were entered, further QC
measures were taken. First the attri-
butes were listed, sorted, and checked
for consistency and accuracy throughout
the dataset. Next, total area for each cov-
erage within a particular watershed was
calculated and compared. Lastly, the data
were compiled into reports for the project
analysis. These reports matched the
attribute code to the description of that
code. Any possible ambiguous codes
were detected and suitably modified
during this process.
Conclusion
These QC procedures were done
throughout the entire dataset. We con-
clude that there is only a minimal amount
of error introduced during digitization of
the mapped data.
Dorothy Mortenson is with Technology Services Corp., Corvallis, OR 97333.
M. R. Church is the EPA Project Officer (see below).
The complete report, entitled "Geographic Information System Documentation of
Watershed Data for Direct/Delayed Response Project — Southern Blue Ridge
Province Database" (Order No. PB 89-219 539/AS; Cost: $13.95, subject to
change) will be available only from:
National Technical Information Service
5285 Port Royal Road
Springfield, VA22161
Telephone: 703-487-4650
The EPA Project Officer can be contacted at:
Environmental Research Laboratory
U.S. Environmental Protection Agency
Corvallis, OR 97333
United States
Environmental Protection
Agency
Center for Environmental Research
Information
Cincinnati OH 45268
Official Business
Penalty for Private Use $300
EPA/600/S3-89/002
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